single-view ambiguity
- Given a camera and an image, we only know the ray corresponding to each pixel.
- We don’t know how far away the object the ray was reflected from
- We don’t have enough constraints to solve for X (depth)
Stereo: given 2 calibrated cameras in different views and correspondences, can solve for X
closers things move more than farther things
depth estimation
- pictorial cues like familiar objects
- shading
- perspective effects
- everything is easier in projective space
- the camera maps 3D world to 2D image - coordinate transformation